This invention relates generally to the provision of refrigeration to a heat load wherein refrigeration is generated and provided to a heat load using a multicomponent refrigerant fluid.
Refrigeration is used extensively in the freezing of foods, production of pharmaceuticals, liquefaction of natural gas, and in many other applications wherein refrigeration is required to provide cooling duty to a heat load. Low temperature refrigeration (less than xe2x88x9280xc2x0 F.) is desirable for use in food freezing applications. The primary advantage of low temperature refrigeration is that it provides for an increased throughout through the freezer that debottlenecks the freezing process.
A recent significant advancement in the field of refrigeration is the development of refrigeration systems using multicomponent refrigerants which are able to generate refrigeration much more efficiently than conventional systems and without the high operating costs incurred with the use of cryogenic liquids. These refrigeration systems, also known as mixed gas refrigerant systems or MGR systems, are particularly attractive for providing refrigeration at very low or cryogenic temperatures such as below xe2x88x9280xc2x0 F.
MGR systems typically have higher initial capital costs than do conventional vapor compression systems. These high initial costs are due primarily to the need for larger or more complicated compressors, vessels and heat exchangers.
Accordingly it is an object of this invention to provide a refrigeration system which will enable the use of an MGR system which has less costly compressors, vessels and/or heat exchangers.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for providing refrigeration comprising:
(A) compressing an ammonia refrigerant fluid, expanding the compressed ammonia refrigerant fluid, and warming the expanded ammonia refrigerant fluid;
(B) compressing a multicomponent refrigerant fluid, and cooling the compressed multicomponent refrigerant fluid in part by indirect heat exchange with the warming ammonia refrigerant fluid to produce cooled compressed multicomponent refrigerant fluid;
(C) expanding the cooled compressed multicomponent refrigerant fluid to produce refrigeration bearing multicomponent refrigerant fluid, and warming the refrigeration bearing multicomponent refrigerant fluid to provide refrigeration to a heat load; and
(D) further warming the refrigeration bearing multicomponent refrigerant fluid to provide additional cooling to the compressed multicomponent refrigerant fluid.
Another aspect of the invention is:
Apparatus for providing refrigeration comprising:
(A) an autorefrigerator heat exchanger, a main compressor, a main expansion device and means for passing multicomponent refrigerant fluid from the main compressor to the autorefrigerator heat exchanger and from the autorefrigerator heat exchanger to the main expansion device;
(B) an auxiliary compressor, an auxiliary expansion device, and means for passing ammonia refrigerant fluid from the auxiliary compressor to the auxiliary expansion device, from the auxiliary expansion device to the autorefrigerator heat exchanger and from the autorefrigerator heat exchanger to the auxiliary compressor;
(C) a heat load device and means for passing multicomponent refrigerant fluid from the main expansion device to the heat load device; and
(D) means for passing multicomponent refrigerant fluid from the heat load device to the autorefrigerator heat exchanger.
A further aspect of the invention is:
Apparatus for providing refrigeration comprising:
(A) a precooler, an autorefrigerator heat exchanger, a main compressor, a main expansion device and means for passing multicomponent refrigerant fluid from the main compressor to the precooler, from the precooler to the autorefrigerator heat exchanger and from the autorefrigerator heat exchanger to the main expansion device;
(B) an auxiliary compressor, an auxiliary expansion device, and means for passing ammonia refrigerant fluid from the auxiliary compressor to the auxiliary expansion device, from the auxiliary expansion device to the precooler and from the precooler to the auxiliary compressor;
(C) a heat load device and means for passing multicomponent refrigerant fluid from the main expansion device to the heat load device; and
(D) means for passing multicomponent refrigerant fluid from the heat load device to the autorefrigerator heat exchanger.
Yet another aspect of the invention is:
Apparatus for providing refrigeration comprising:
(A) an autorefrigerator heat exchanger, a main compressor, a main expansion device and means for passing multicomponent refrigerant fluid from the main compressor to the autorefrigerator heat exchanger and from the autorefrigerator heat exchanger to the main expansion device;
(B) an auxiliary compressor, an auxiliary expansion device, and means for passing ammonia refrigerant fluid from the auxiliary compressor to the auxiliary expansion device, from the auxiliary expansion device to the autorefrigerator heat exchanger and from the autorefrigerator heat exchanger to the auxiliary compressor;
(C) means for passing multicomponent refrigerant fluid from the main expansion device to the autorefrigerator heat exchanger; and
(D) means for providing a heat load to the autorefrigerator heat exchanger.
As used herein the term xe2x80x9cexpansionxe2x80x9d means to effect a reduction in pressure.
As used herein the term xe2x80x9cexpansion devicexe2x80x9d means apparatus for effecting expansion of a fluid.
As used herein the term xe2x80x9ccompressorxe2x80x9d means apparatus for effecting compression of a fluid.
As used herein the term xe2x80x9cmulticomponent refrigerant fluidxe2x80x9d means a fluid comprising two or more species and capable of generating refrigeration.
As used herein the term xe2x80x9crefrigerationxe2x80x9d means the capability to reject heat from a subambient temperature system.
As used herein the term xe2x80x9crefrigerant fluidxe2x80x9d means fluid in a refrigeration process which undergoes changes in temperature, pressure and possibly phase to absorb heat at a lower temperature and reject it at a higher temperature.
As used herein the term xe2x80x9cvariable load refrigerantxe2x80x9d means a mixture of two or more components in proportions such that the liquid phase of those components undergoes a continuous and increasing temperature change between the bubble point and the dew point of the mixture. The bubble point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the liquid phase but addition of heat will initiate formation of a vapor phase in equilibrium with the liquid phase. The dew point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the vapor phase but extraction of heat will initiate formation of a liquid phase in equilibrium with the vapor phase. Hence, the temperature region between the bubble point and the dew point of the mixture is the region wherein both liquid and vapor phases coexist in equilibrium. In the preferred practice of this invention the temperature differences between the bubble point and the dew point for a variable load refrigerant generally is at least 10xc2x0 C., preferably at least 20xc2x0 C., and most preferably at least 50xc2x0 C.
As used herein the term xe2x80x9cheat loadxe2x80x9d means a stream or object that requires a reduction in energy, or removal of heat, to lower its temperature or to keep its temperature from rising.
As used herein the term xe2x80x9cammonia refrigerant fluidxe2x80x9d means a refrigerant fluid comprising ammonia.
As used herein the term xe2x80x9cautorefrigerator heat exchangerxe2x80x9d means a heat exchanger in a multicomponent refrigerant fluid cycle wherein a high pressure refrigerant stream is cooled against a returning low pressure refrigerant stream. The autorefrigerator heat exchanger may include other process streams.